Field
Example embodiments described herein are generally directed to dewarping, and more specifically, dewarping from use of a stereo camera or a mobile phone camera capturing a sequence of images.
Related Art
In the related art, documents can be “scanned” by utilizing digital cameras or mobile devices to capture images of documents. Compared with flatbed scanners, photos of documents may suffer from various issues including perspective distortion, warping, uneven lighting, etc.
One scenario of interest is to use a handheld consumer-grade compact 3D stereo camera to capture images of page spreads from a document such as a book. For example, a student can use the camera to take notes from books in a library, without having to go to the copy machine and potentially damage the book spines during the copying process. Another example is the digitization of documents in storage, in which bounded or loose paper records are often not in condition to be used with flat-bed or V-bed book scanners without incurring damage. Being able to use the compact cameras on-site is another benefit.
In related art implementations for non-3D capture and dewarping of book page images, the 3D information is computed by detecting curved text lines or other content features, and the dewarping is based on models including the cylinder model.
For 3D capture, related art implementations utilize structured light and multiple cameras. Structured light can sense highly accurate 3D information; however, related art systems utilizing structured light may require extensive hardware. The multiple camera (including stereo camera) approach of the related art can be implemented in a less complex system, but may not be as robust due to the dependence on the page areas containing visible text content or texture.
Some dewarping methods in the related art that have been used with structured light include energy minimization and conformal mapping. However, such related art implementations may require highly accurate 3D information and may thereby be difficult to implement with low-cost consumer grade stereo cameras. Such related art systems utilize a stereo capture system that uses special apparatus with left and right light sources, or a conformal method applied in a stereo system without structured light.
It would also be advantageous to use devices, such as a mobile phone camera, which may be more commonly available than a handheld consumer-grade compact 3D stereo camera, to capture images of page spreads.